CN218275499U - High-power nanosecond extra-cavity quintupling frequency laser - Google Patents

Abstract

The utility model discloses an outer five times frequency laser instrument of high power nanosecond chamber. Firstly, two high-power pump lights are converged into a laser crystal after passing through a pump coupling system, and the laser crystal compensates the thermal lens effect of the laser crystal through a plurality of lenses, so that the laser crystal can generate high-power nanosecond laser under the action of the high-power pump lights. And secondly, a first sum frequency crystal and a second sum frequency crystal are arranged in the laser cavity body, and the output of high-power second-third-octave light is generated by utilizing the intra-cavity high peak power characteristic. Then, the output high-power second-third-frequency light is subjected to adjustment of the polarization state and the spot size outside the laser cavity. Finally, the combined light passes through a quintupling crystal to generate high-power nanosecond quintupling laser.

Description

High-power nanosecond extra-cavity quintupling frequency laser

Technical Field

The utility model relates to the laser field especially involves the design in solid nanosecond higher order frequency multiplication field.

Background

The deep ultraviolet light source with the wave band of 210nm has important application in the fields of semiconductor photoetching, high-density storage, high-precision spectral analysis and the like. Early deep ultraviolet lasers mainly used ArF quasi-molecular gas lasers, but these lasers had the disadvantages of high cost, low repetition frequency, wide line width, poor beam quality, etc. The solid nanosecond quintupling 213nm ultraviolet laser can well solve the problems of the excimer laser and has the characteristics of low cost, high repetition frequency, narrow line width, excellent light beam quality and the like. Therefore, the research and development of the nanosecond-level quintupling frequency deep ultraviolet laser with simple structure and high stability have great propulsion effect on the semiconductor processing industry.

Disclosure of Invention

For complicated devices such as picosecond ultraviolet, femto second ultraviolet, the utility model relates to a simple structure, the high power nanosecond intracavity quintuple frequency laser that the reliability is high.

The utility model discloses mainly constitute for two parts from the principle, the first part is high power nanosecond triple frequency two and produces the system, and the second part is the frequency sum system of quintuple.

The high-power nanosecond extra-cavity quintuple frequency laser is characterized by comprising a high-power nanosecond triple frequency generation system, wherein the high-power nanosecond triple frequency generation system is a high-power double-end pump pumping system and consists of a total reflection mirror (11), a Q-switch (12), a first lens (131), a laser crystal (14), a second lens (132), a first dichroic mirror (15), a sum frequency crystal I (16), a sum frequency crystal II (17), a multi-wavelength reflecting mirror (18) and a high-power pumping source.

The two high-power pump sources are respectively converged in the laser crystal (14) through a first pump coupling system (191) and a second pump coupling system (192). The pumping system adopts pumping light with 878nm or 888nm, is used for reducing the quantum defect of the laser crystal and can generate higher pumping power. The corresponding laser crystal (14) is a neodymium-doped particle crystal, the length of the laser crystal is about 50mm, the laser crystal is used for completely absorbing pump light, and the concentration of the corresponding crystal is adjusted according to design requirements.

In the high-power nanosecond-tripled frequency generation system, the first lens (131) and the second lens (132) can be plano-convex or lenses with corresponding curvatures, the curvature of the lenses and the coating requirements are adjusted according to requirements, and the purpose is mainly to compensate the thermal focal length of the crystal and fold and compress an optical path.

In the high-power nanosecond-triple frequency generation system, a sum frequency crystal I (16), a sum frequency crystal II (17) are a triple frequency crystal and a double frequency crystal, and the sum frequency crystal II (17) carries out I-type phase matching by using an LBO crystal to carry out frequency doubling; and the sum frequency crystal I (16) uses LBO crystal to carry out class II phase matching to carry out sum frequency, the frequency doubling crystal selection is not limited to the LBO crystal, and the crystals with the same function are all included in the utility model. All the crystals are placed in a device using TEC for accurate temperature control, and are used for accurate control of the light output power.

In the high-power nanosecond triple frequency generation system, the first dichroic mirror (15) is a low-pass filter and is used for enabling fundamental frequency light to oscillate in the cavity, and enabling high-order sum frequency light to be emitted through the first dichroic mirror (15) so as to facilitate subsequent sum frequency. The multi-wavelength reflector (18) is a multi-point high-reflection mirror and is used for reflecting fundamental frequency light and frequency-doubled light.

The first dichroic mirror (15) and the multi-wavelength reflector (18) are plano-concave lenses and plano-flat lenses which are matched with each other to change the size of light spots converged on the sum frequency crystal, the light spots converged on the crystal are properly controlled, and the sum frequency efficiency can be increased.

The high-power nanosecond extra-cavity quintupling frequency laser is characterized by comprising a quintupling frequency sum frequency system, wherein the quintupling frequency sum frequency system consists of a second dichroic mirror (21), a second frequency doubling light path system, a third dichroic mirror (24), a quintupling frequency crystal (25), a beam splitting device (26) and a light blocking device (27).

The double-frequency optical path system and the triple-frequency optical path system are characterized in that the propagation distances of the two optical paths are equal, and meanwhile, the focuses of the two-frequency light and the triple-frequency light meet the coincidence relation.

The frequency doubling optical path system is characterized in that frequency doubling light transmits and propagates through the second dichroic mirror (21), changes the propagation direction through the second reflecting mirror (22), is converged through the second coupling mirror (23), and is reflected through the third dichroic mirror (24) to enter the quintupling crystal (25).

The propagation characteristic of the frequency tripling optical path system is that frequency tripling light is reflected and propagated after passing through the second dichroic mirror (21), the propagation direction is changed after passing through the first reflecting mirror (31), the polarization state of the frequency tripling light after changing the propagation direction is changed through the wave plate (32), then the frequency tripling light is converged through the first coupling mirror (33), and finally the frequency tripling light enters the frequency quintupling crystal (25) after passing through the third dichroic mirror (24).

In a quintupling frequency sum frequency system, the second dichroic mirror (21) is a high-pass filter and is used for transmitting the frequency-doubled light and reflecting the frequency-tripled light. And the third dichroic mirror (24) for beam combination is a low-pass filter and is used for double-frequency light reflection and triple-frequency light transmission and is used for beam combination of light beams.

Wherein, the wave plate (32), the first coupling mirror (33) are plated with a triple frequency reflection reducing coating, and the second coupling mirror (23) is plated with a double frequency reflection reducing coating. The incidence end face of the quintuple frequency crystal (25) can be coated with a double-triple frequency anti-reflection film, and the light-emitting surface is not coated with a film.

Wherein the quintupling frequency crystal (25) is a deep ultraviolet sum frequency crystal, and a BBO crystal or a CLBO crystal is used.

And finally, the frequency-doubled and frequency-doubled light and the frequency-doubled and frequency-doubled light are split after passing through a beam splitting device (26) with a designed angle, and if the frequency-doubled and frequency-doubled light is not used, a light blocking device (27) is required for collection.

Drawings

Fig. 1 is a diagram of a corresponding high power nanosecond extra-cavity quintupling laser.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. It should be understood that the specific examples described herein are for purposes of illustration only and are not intended to limit the invention.

The system is composed of two parts, namely a high-power nanosecond-triple frequency generation system and a quintuple frequency sum frequency system.

First part high power nanosecond triple frequency generation system, at first overall structure be a bi-polar pump planoconvex unstable resonator and produce the two triple frequency light of high power, totally reflect mirror (11) and be the monochromatic high reflection mirror, the utility model discloses well recommendation 1064nm wavelength single point high reflection mirror, first lens (131), second lens (132) are planoconvex low pass high reflection mirror, recommend to use high 888nm laser of passing through, high anti 1064nm laser parameter, reflection angle is less than 13.

And the sum frequency crystal II (17) is a frequency doubling crystal, LBO is recommended to be used as the frequency doubling crystal, but the sum frequency crystal is not limited to the LBO crystal, the length of the crystal is recommended to be longer than 10mm, and the coating mode is 1064nm and 532nm high-transmittance. The LBO crystal uses TEC to control temperature accurately, thereby realizing the purpose of high-efficiency frequency doubling and tunable frequency doubling power. The sum frequency crystal I (16) is a frequency tripling sum frequency crystal, LBO is recommended to be used as the sum frequency crystal, but the sum frequency crystal is not limited to the LBO crystal, the length of the crystal is recommended to be longer than 20mm, the coating mode is 1064nm,532nm and 355nm high-transparency, and the LBO has the advantages of small walk-off, excellent light beam quality, high damage resistance and the like.

The 888nm laser pumping source is recommended to be used as the pumping source, the main advantages are that quantum loss is low, less heat can be generated after YVO4 is Nd, and intracavity frequency doubling light can be generated. The Q-switch (12) accumulates energy by switching on and off the light, and finally the output of the laser with high peak power in Q-switching is realized.

The all-reflection mirror (11), the first lens (131), the laser crystal (14), the second lens (132), the first dichroic mirror (15) and the multi-wavelength reflector (18) form a fundamental frequency resonant cavity. The first dichroic mirror (15) is an optical filter, a low-pass high-reflection film system is recommended to be plated by using a plano-concave lens or a plano-flat lens, and the main purpose is two points, namely, the first dichroic mirror and the multi-wavelength reflector (18) are matched for changing the size of a light spot converged on a frequency doubling crystal, the light spot converged on frequency doubling is properly controlled, and the frequency doubling efficiency can be increased; 2. the film layer is designed into a lens with high transmission of the second and third frequency lights and high reflection of the basic frequency light, can be used for harmonic output and is used for outputting the second frequency light and the third frequency light, and the basic frequency light continues to resonate in the cavity. The proposal of using the coating with 532nm,355nm high transmittance and 1064nm high reflectance is recommended.

The multi-wavelength reflector (18) is a back cavity mirror of the laser and is used for reflecting the fundamental frequency light and the frequency doubling light, and the returned fundamental frequency light and the frequency doubling light generate triple frequency light in the neutralization frequency of the sum frequency crystal I (16). The multi-wavelength reflector (18) can be a plano-concave lens or a plano-plano mirror, aiming at controlling the size of light spots in the crystal by matching with the first dichroic mirror (15), and the recommended lens coating scheme is 532m and 1064nm high-reflection coating parameters.

The utility model discloses YVO4 crystal is used to laser working crystal (14) is recommended to the scheme, and the selection of crystal has a plurality ofly, needs use the scene according to the customer, and the single pulse energy, repetition frequency and pumping source pumping parameter are synthesized and are selected, the utility model provides a crystal not only limits to the Nd YVO4 crystal, and relevant 1um wave band neodymium ion laser crystal is in the utility model discloses the protection within range.

The corresponding frequency doubling process is that the fundamental frequency light returned from the multipoint reflector (18) is firstly frequency doubled in the sum frequency crystal II (17) to generate frequency doubled light, when the laser continues to propagate, the frequency doubled light and the residual fundamental frequency light are neutralized in the sum frequency crystal I (16) to generate triple frequency light, finally the double triple frequency light is emitted at the position of the first dichroic mirror (15), and the residual fundamental frequency light continues to oscillate in the cavity.

In the present invention, YVO4 crystal is preferably used as the laser crystal (14), the C-axis direction is parallel to the paper surface, and the polarization direction of the final fundamental light is parallel to the paper surface. The sum frequency crystal II (17) is an LBO crystal, the fundamental frequency light generates double frequency light through the double frequency crystal by using I-type phase matching, and the cutting direction of the crystal is Theta =90; phi =10.8, the crystal is a normal temperature crystal, the frequency doubling efficiency is accurately controlled by the TEC, and the polarization direction of the frequency doubled light is vertical to the plane of the paper. The frequency tripling crystal is LBO crystal, fundamental light and frequency doubler light are generated in frequency tripling light by II phase matching in the sum frequency crystal I (16). The cutting direction of the frequency tripling crystal is Theta =44; phi =90, 50 ℃ crystal temperature, main purpose to prevent deliquescence, and polarization direction of frequency tripled light after sum frequency is parallel to paper surface.

Finally, the frequency-doubled light and the frequency-doubled light are output through the first dichroic mirror (15), wherein the light output power can be controlled through the temperature control of the TEC, the power ratio of the frequency-doubled light to the frequency-doubled light which can be emitted under the ideal condition is 2:1, the frequency-doubled light cannot be completely converted into the frequency-tripled power due to the influence of the walk-off equivalent, only a specific conversion proportion is needed, and finally the proportion of the frequency-tripled light to the frequency-doubled light is controlled to be 3:2 by adjusting the temperature control.

The second part of the quintuple frequency doubling sum frequency system is shown in fig. 1, and the main sum frequency mode is that the two-three frequency doubling light enters a quintuple frequency crystal after being adjusted outside a cavity to realize the sum frequency output of the quintuple frequency light. The light emitting second and third frequency multiplication in the laser device is incident on a second dichroic mirror (21), the second dichroic mirror (21) mainly has the function of splitting the two-frequency multiplication light and the three-frequency multiplication light, and the recommended coating scheme is a 532nm high-transmittance, 355nm high-reflectance and 45-degree reflection coating scheme.

After passing through the second dichroic mirror (21), the double frequency passes through the second reflecting mirror (22), the propagation direction is changed, and then the light is converged through the second coupling lens (23). The focal length of the second coupling lens (23) is not particularly small, preferably around 200mm, and is then reflected by a third dichroic mirror (24) into a quintupling crystal (25).

The triple frequency light reflected by the second dichroic mirror (21) is controlled in the propagation direction by the first reflecting mirror (31) and then passes through a wave plate (32), wherein the wave plate (32) is a half wave plate of the triple frequency light, and the optical axis direction and the polarization direction of incident light form 45 degrees, so that the polarization direction of the incident light becomes perpendicular to the original direction after passing through the wave plate. The light with changed polarization direction is then converged by a first coupling mirror (33), and the converged light enters the crystal through a third dichroic mirror (24), wherein the focal length of the first coupling mirror (33) is the same as that of the second coupling mirror (23).

The frequency-doubled light and the frequency-tripled light respectively transmitted from the two optical paths are converged into a quintupling frequency crystal (25) after passing through the same third dichroic mirror (24), and quintupling frequency laser is generated in the quintupling frequency crystal (25) by using I-type phase matching.

When the sum frequency is carried out in the quintuple frequency crystal, two points need to be ensured, namely coincidence of the sum frequency light in space and time.

The spatial coincidence of two sum frequency lights is that a second reflecting mirror (22) in a double-frequency-multiplication walking light path is respectively adjusted, a third dichroic mirror (24) and a second dichroic mirror (21) in a triple-frequency-multiplication walking light path are adjusted, the coincidence of the light path at the spatial position is realized by a first reflecting mirror (31), according to the definition of spatial freedom, when two lenses can be freely adjusted in each light path, the direction of light transmission can be accurately controlled, so that two lenses can respectively adjust the own propagation direction in the double-frequency-multiplication light path, the coincidence of the propagation directions in the space can be satisfied, the distance between a second coupling mirror (23) and a first coupling mirror (33) relative to a crystal is adjusted simultaneously, and the coincidence of two focuses can be realized.

In addition, the two sum-frequency lights also need to meet the requirement of coincidence in time, namely, the optical path difference between the two optical paths is approximate to zero, so that the time coincidence can be met. Because the utility model discloses a nanosecond laser, according to the design of preceding stage laser, the pulse width of the two multiples of laser and the triple frequency light is about 20ns, calculates according to the velocity of light, and the error of two light paths only reaches the level more than 1 meter and just can produce the influence of essence to time coincidence. Therefore, the optical path distances after separation are ensured to be equal as much as possible through ruler measurement, and the requirement of corresponding frequency doubling efficiency can be met.

The quintupling frequency crystal (25) is simple to select, only BBO and CLBO on the market can be used commercially, and BBO can be used as a sum frequency crystal with excellent deep ultraviolet comprehensively. However, BBO crystals have two major drawbacks that cannot be avoided. Firstly, BBO crystal has a relatively large absorption effect on deep ultraviolet; secondly, the walk-off of BBO crystals is relatively severe. In order to reduce the influence of the two defects of the BBO crystal on the beam quality as much as possible, beam-shrinking convergence is adopted to increase the corresponding frequency doubling efficiency. The spot size in the crystal can be well controlled by well controlling the focal lengths of the second coupling mirror (23) and the first coupling mirror (33), so that the frequency doubling efficiency is properly improved. The length of the crystal is calculated to recommend that the crystal is not more than 6mm, so that the spot deformation of the crystal can be relatively controlled.

The sum frequency deep ultraviolet laser is then separated from the incident light by a beam splitting device (26), and then beam shaping can be performed on the deep ultraviolet light if necessary to reduce astigmatism of the deep ultraviolet light, but the beam shaping can reduce the light output power, and finally balancing is performed according to the use condition.

The corresponding polarization direction and crystal cut direction. The double frequency and triple frequency emitted from the laser cannot directly sum frequency to generate quintupled deep ultraviolet light, and the polarization direction of the triple frequency needs to be changed to meet the phase matching condition. The triple frequency light emitted integrally is parallel to the paper surface, the polarization direction is changed to be vertical to the paper surface after passing through the wave plate (32), when the triple frequency light enters the quintuple frequency crystal BBO, the double frequency light and the triple frequency light are both vertical to the paper surface, and the quintuple frequency light after the sum frequency is parallel to the paper surface. After the quintupled frequency light parallel to the paper surface passes through two angle-distribution beam splitting devices (26), the loss of deep ultraviolet light can be reduced as much as possible.

Wherein the cutting direction of the quintupled frequency crystal is Theta =69.7 degrees, phi =0 degrees, and because the BBO crystal is not very sensitive to temperature, the BBO crystal does not need to have high requirement on the temperature during sum frequency. When the frequency doubling and frequency tripling temperatures of the laser are changed, the proportion of laser incident into the BBO crystal can be changed, and the frequency doubling and frequency tripling temperatures are finally determined by monitoring the power of the emergent frequency quintupling laser.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims (8)

1. The high-power nanosecond-tripler frequency-quintupling laser is characterized by comprising a high-power nanosecond-tripler frequency generation system and a quintupled frequency sum system, wherein the high-power nanosecond-tripler frequency generation system is a high-power solid nanosecond laser and comprises a total reflection mirror (11), a Q-switch (12), a first lens (131), a laser crystal (14), a second lens (132), a first dichroic mirror (15), a sum frequency crystal I (16), a sum frequency crystal II (17), a multi-wavelength reflecting mirror (18) and two high-power pumping coupling systems, and the quintupled frequency sum system comprises a second dichroic mirror (21), a frequency doubling optical path system, a triple optical path system, a third dichroic mirror (24), a quintupled frequency crystal (25), a beam splitting device (26) and a light blocking device (27).

2. The high-power nanosecond extra-cavity quintupling laser device as claimed in claim 1, wherein the high-power pump coupling system is a double-end pump coupling system, the two high-power fiber coupling modules pump the laser crystal (14) together through the first coupling system (191) and the second coupling system (192), respectively, and the high-power pump coupling system adopts 878nm or 888nm pump light for reducing quantum loss of the laser crystal and generating higher pump power and lower thermal effect.

3. The high power nanosecond extra-cavity quintupling laser according to claim 1, characterized in that it comprises a first dichroic mirror (15), said first dichroic mirror (15) being a low pass filter for letting fundamental frequency light oscillate in the cavity, and letting higher order sum frequency light be output through the first dichroic mirror (15).

4. The high power nanosecond extra-cavity quintupling laser of claim 1, comprising a frequency doubling optical path system and a frequency tripling optical path system, wherein the optical path distances of the frequency doubling optical path system and the frequency tripling optical path system are equal.

5. The high power nanosecond extra-cavity quintupling laser as claimed in claim 1, characterized by comprising a frequency doubling optical path system and a frequency tripling optical path system, in which the frequency doubling optical path system and the frequency tripling optical path system the frequency doubling light and the frequency tripling light coincide spatially when entering the quintupling crystal.

6. The high-power nanosecond extra-cavity quintupling laser device according to claim 1, characterized by comprising a frequency doubling optical path system and a frequency tripling optical path system, wherein the frequency doubling optical path system is characterized in that the frequency doubling light is transmitted and propagated through the second dichroic mirror (21), the propagation direction is changed through the second reflecting mirror (22), the frequency doubling light is converged through the second coupling mirror (23), and then reflected and propagated through the third dichroic mirror (24), and then enters the quintupling crystal (25), the frequency tripling optical path system is characterized in that the frequency tripling light is reflected and propagated through the second dichroic mirror (21), the propagation direction is changed through the first reflecting mirror (31), and then the frequency tripling light after changing the propagation direction first changes the polarization state through the wave plate (32), then converged through the first coupling mirror (33), and finally enters the quintupling crystal (25) through the third dichroic mirror (24).

7. The high power nanosecond extra-cavity quintupling laser according to claim 1, characterized in that it comprises a quintupling crystal (25), said quintupling crystal (25) being a deep ultraviolet sum frequency crystal, the crystal being chosen as a BBO crystal or a CLBO crystal.

8. The high power nanosecond extra-cavity quintupling laser according to claim 1, characterized by comprising a second dichroic mirror (21) and a third dichroic mirror (24), said second dichroic mirror (21) being a high pass filter for transmission of frequency doubled light and reflection of frequency tripled light, said third dichroic mirror (24) being a low pass filter for reflection of frequency doubled light and transmission of frequency tripled light for beam combining.

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